The function Issimilar(A, B) is a placeholder for the boolean valued function that returns true if A is similar to B and false otherwise. It is used in conjunction with either mod or evala.

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If called in the form Issimilar(A, B,'P'), then P will be assigned a transformation matrix such that .

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The call Issimilar(A, B) mod p determines if A is similar to B modulo p which is a prime integer. The entries of A and B must have rational coefficients or coefficients from an algebraic extension of the integers modular p.

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The call evala(Issimilar(A, B)) determines if A is similar to B where the entries of A and B are algebraic numbers (or functions) defined by RootOfs.